What is the difference between Catholic and Protestant?
Anyone who has ever read the Scriptures knows that Jesus claimed to be God. One example will suffice:
John 8:58 Jesus said to them: Amen, amen I say to you, before Abraham was made, I am.
And Jesus provided the evidence to prove that He is God by raising the dead, healing the sick, multiplying the fish and the loaves and turning water to wine. These things were testified by many witnesses. And His followers, many of them could also perform such miracles as he empowered them to perform.
So, if Jesus was simply a man as some claim and he was killed on the Cross. Then his sacrifice amounted to a mad man or a liar who died for a lie. And the sacrifice does not atone for all the sins of humanity.
But, If Jesus is God as He claimed and proved by His miracles, then His sacrifice on the Cross amounts to exactly what Scripture says it does:
Isaias 53 5 But he was wounded for our iniquities, he was bruised for our sins: the chastisement of our peace was upon him, and by his bruises we are healed.
And this Old Testament prophecy can only refer to one person:
Wisdom 2 12 Let us therefore lie in wait for the just, because he is not for our turn, and he is contrary to our doings, and upbraideth us with transgressions of the law, and divulgeth against us the sins of our way of life. 13 He boasteth that he hath the knowledge of God, and calleth himself the son of God. 14 He is become a censurer of our thoughts. 15 He is grievous unto us, even to behold: for his life is not like other men's, and his ways are very different. 16 We are esteemed by him as triflers, and he abstaineth from our ways as from filthiness, and he preferreth the latter end of the just, and glorieth that he hath God for his father. 17 Let us see then if his words be true, and let us prove what shall happen to him, and we shall know what his end shall be. 18 For if he be the true son of God, he will defend him, and will deliver him from the hands of his enemies. 19 Let us examine him by outrages and tortures, that we may know his meekness and try his patience. 20 Let us condemn him to a most shameful death: for there shall be respect had unto him by his words.
I’ll give you three guesses, “Who?”